4.3

Question 1

What increases the proportion of successful collisions?

Answer 1

Increasing temperature and adding a catalyst.

Question 2

What is the test for oxygen gas?

Answer 2

A lit splint will relight.

Question 3

What is the test for carbon dioxide?

Answer 3

If you bubble it through limewater, it will turn cloudy.

Question 4

Why would a student place cotton wool on the top of their flask?

Answer 4

So no water can splash out and only gas can escape.

Question 5

In the test *, why would the rate of reaction decrease?
*(calcium carbonate and an excess of dilute hydrochloric acid)

Answer 5

The concentration of acid decreases * & less frequent collisions.
*(/ amount of CaCo3 decreases)

Question 6

The student uses the same mass of a substance but in smaller pieces how would this affect the rate of reaction?

Answer 6

It will increase the rate of reaction,
the surface area of the substance is increased,
more of the reactant is exposed,
more frequent / more successful collisions per unit time

Question 7

more frequent collisions per ? ?

Answer 7

unit time

Question 8

what is a suitable catalyst for * this experiment?
*(catalyst affects hydrogen peroxide decrease)

Answer 8

manganese (IV) oxide

Question 9

how will a catalyst affect the rate of an experiment?

Answer 9

rate of reaction will increase,
catalyst provides an alternate path route,
with a lower activation energy.

Question 10

the pressure is decreased in * an experiment, how will this affect the volume produced in 30 secs?
*(hydrogen iodide)

Answer 10

the volume will decrease.

Question 11

what is a suitable piece of equipment to measure the volume with:?

Answer 11

a gas syringe.

Question 12

why can you reuse catalysts?

Answer 12

they are not used up in the reaction.

Question 13

why is method 1 (the rate using volume of gas) collecting under water bad?

Answer 13

because gas is lost between adding the marble and replacing the bung.
gas can dissolve in water.

Question 14

why is method 2 (the rate using volume of gas)
using a gas syringe bad?

Answer 14

because gas is lost between adding the marble and replacing the bung.

Question 15

why is method 3 (the rate using volume of gas)
change in mass bad?

Answer 15

it is a slower method than collecting the gas.

Question 16

what is the reaction rate and how is it measured?

Answer 16

The rate of a reaction is the measure of the change in quantity of reactants or products per unit time (usually per second)

Question 17

collision theory states that for a reaction to occur:

Answer 17

Particles must have at least the activation energy.
Particles must collide.

Question 18

Ways to speed up a chemical reaction:

Answer 18

Increasing temperature.
Increase surface area of solids.
Increasing concentrations of solutions.
Increasing pressure of gases.
Add a catalyst.

Question 19

How does increasing concentration of a solution alter reaction rate?

Answer 19

it increases the RATE of a reaction
there are more PARTICLES in the same volume
there are more FREQUENT COLLISIONS
so there are more SUCCESSFUL FREQUENT COLLISIONS PER UNIT TIME

Question 20

COLLISION THEORY
HIGHER SOLID SURFACE AREA increases rate because:

Answer 20

MORE OF THE SOLID IS EXPOSED to the OTHER PARTICLES
COLLISION FREQUENCY IS HIGHER
MORE SUCCESSFUL COLLISIONS PER UNIT TIME

Question 21

COLLISION THEORY
HIGHER SOLUTION CONCENTRATION / GAS PRESSURE increases rate because:

Answer 21

MORE PARTICLES PER UNIT VOLUME
COLLISION FREQUENCY IS HIGHER
MORE SUCCESSFUL COLLISIONS PER UNIT TIME

Question 22

COLLISION THEORY
HIGHER TEMPERATURE increases rate because:

Answer 22

particles have more KINETIC ENERGY
% OF COLLISIONS WITH ENOUGH ENERGY IS HIGHER
MORE SUCCESSFUL COLLISIONS PER UNIT TIME

Question 23

COLLISION THEORY
CATALYSTS increase rate because:

Answer 23

provide an ALTERNATIVE ROUTE with a LOWER ACTIVATION ENERGY
% OF COLLISIONS WITH ENOUGH ENERGY IS HIGHER
MORE SUCCESSFUL COLLISIONS PER UNIT TIME

Question 24

METHOD FOR CROSS UNDER FLASK SODIUM THIOSULPHATE

Answer 24

measure 20cm3 HCl into 100cm3 conical flask
conical flask ontop of black cross
30cm3 distilled water in flask
10cm3 Na2SO3 to flask and start times
swirl the flask thoroughly for few seconds
stop timer when u can no longer see the cross
pour contents into fume-cupboard sink
rinse flask twice with cold water
repeat 3 times using different volumes of water and Na2S2O3

Question 25

INDEPENDANT CONTROL DEPENDANT VARIABLE FOR SODIUM THIOSULPHATE

Answer 25

INDEPENDANT: CONCENTRATION OF NA2S2O3
DEPENDANT: TIME TAKEN FOR CROSS TO DISAPPEAR
CONTROL: TEMP, VOLUME, CONC OF HCl, AMOUNT OF SWIRLS ETC